Method of patterning magnetic products using chemical reaction

ABSTRACT

A method of patterning magnetic material includes forming a ferromagnetic material layer containing one element selected from the group consisting of Fe, Co and Ni on a substrate, selectively masking a surface of the ferromagnetic material layer, and making nonferromagnetic. The making nonferromagnetic step includes exposing an exposed portion in halogen-containing reaction gas, changing magnetism of the exposed portion and a lower layer thereof by chemical reaction, and making the exposed portion a nonferromagnetic material region. A magnetic recording medium is fabricated by using the magnetic material patterning method and includes a plurality of recording regions made of ferromagnetic materials, each containing at least one element selected from the group consisting of Fe, Co and Ni, and a nonferromagnetic material region for separating the recording regions from each other. The nonferromagnetic material region is a compound region of the ferromagnetic material and halogen.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation application of U.S. application Ser.No. 10/108,431 filed on Mar. 29, 2002, now U.S. Pat. No. 6,841,224,which is based upon and claims the benefit of priority from the priorJapanese Patent Applications No. 2001-102215 filed on Mar. 30, 2001 andNo. 2001-399848 filed on Dec. 28, 2001, the entire contents of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a high-density magnetic recordingtechnology and, more particularly, to a method of patterning magneticproducts, magnetic recording media such as patterned media produced bythis method, and other magnetic products, and to a magnetic recordingapparatus equipped with such magnetic recording media.

2. Description of the Related Art

In recent years, because of an increase in a surface recording densityof a magnetic recording medium along with an increased recordingcapacity of a hard disk drive (referred to as HDD, hereinafter), eachrecording bit size on the magnetic recording medium has become extremelyminute, about several 10 nm. To obtain a reproducing output from such aminute recording bit, saturation magnetization and a film thickness aslarge as possible must be secured for each bit. However, the minuterecording bit reduces a quantity of magnetization per bit, and therearises a problem that is loss of magnetization information due tomagnetization reversal by “thermal fluctuation”.

Generally, it is said that this “thermal fluctuation” has a largereffect as a value of Ku·V/kT (Ku: a magnetic anisotropy constant, V: aminimum unit volume of magnetization, k: Boltzman's constant, T: anabsolute temperature) is smaller, and it is empirically said thatmagnetization reversal occurs because of “thermal fluctuation” atKu·V/kT<100.

In the case of a magnetic recording medium of a longitudinal magneticrecording mode, since a demagnetization field becomes strong in arecording bit of a high recording density region, the medium tends to beaffected by “thermal fluctuation” even while a magnetic particle size isrelatively large. On the other hand, in the case of a magnetic recordingmedium of a perpendicular magnetic recording mode, since growth of amagnetic particle in a film thickness direction enlarges a minimum unitvolume of magnetization V while keeping a particle size of a mediumsurface small, the effect of “thermal fluctuation” can be suppressed.However, if a density of the HDD is increased much more in the future,there may be a limit to resistance to thermal fluctuation even for theperpendicular magnetic recording mode.

As a method for solving the problem of the thermal fluctuationresistance, a magnetic recording medium called “patterned medium”attracts attention. The patterned medium generally means a magneticrecording medium in which a plurality of magnetic material regions to berecording bit units are independently formed in a nonmagnetic materiallayer. In a general patterned medium, for the nonmagnetic materiallayer, for example, an oxide such as SiO₂, Al₂O₃ or TiO₂, a nitride suchas Si₃N₄, AlN or TiN, carbide such as TiC, and boride such as BN areused, and ferromagnetic material regions are selectively formed in thesenonmagnetic material layers.

In the patterned medium, since the ferromagnetic material regions whichare the recording bit units are independent of each other, interferencebetween the respective recording bits can be prevented. Therefore, thepatterned medium is advantageous for reducing recording loss and noiseswhich are caused by adjacent bits. Moreover, patterning increasesresistance of domain wall movement (pinning effect of domain wall),making it possible to improve magnetic properties.

On the other hand, in the case of the HDD, positioning of a magnetichead in a target position (target track) on the magnetic recordingmedium or moving speed is controlled based on servo informationpre-recorded on the magnetic recording medium. Generally, the servoinformation is recorded in each of servo regions (servo sectors)radially provided at predetermined intervals in a circumferentialdirection on the magnetic recording medium.

Normally, writing of the servo information is carried out by using aservo writing device called a servo track writer. After assembling themagnetic recording medium and the magnetic head into a casing of a HDDmain body, the servo information is written. However, as a recordingdensity of the HDD becomes much higher, the quantity of the servoinformation is increased proportionately thereto. Then, an area of theservo region on the magnetic recording medium is consequently increased,reducing an area of an effective recording region (data region) incontradiction.

On the other hand, studies have recently been conducted on a magneticrecording medium structure of a “deep layer servo system” which has aservo region buried in a deep layer different from a magnetic recordinglayer. In this structure, since the recording region and the servoregion can be formed by being laid on each other, a full surface of themagnetic recording medium can be used as the recording region, and theservo region can also be formed on the full surface of the magneticrecording medium. Thus, without sacrificing the recording region, themagnetic head is enabled to perform highly accurate tracking at anypoint on the disk.

To fabricate the above-described patterned medium, it is necessary toform fine magnetic material patterns in a large area. On the other hand,a magnetic random access memory (MRAM) has recently attracted attentionas a new nonvolatile memory element. Manufacturing of the MRAM alsonecessitates highly integrated magnetic material patterning.

Conventionally, for such magnetic material patterning, the followingfour processes have mainly been employed: first, a process for forming amagnetic material thin film to be fabricated; second, a photolithographyprocess for forming a resist film on the magnetic material thin film,and for forming a pattern on the resist film by using photon energy,electron beams, ion beams or the like; third, a process for etching themagnetic material thin film using the resist pattern as a mask; andfourth, a process for removing remaining resists or residuals left afterthe etching. Among the above processes, the thin film formation process,the photolithography process, and the residual removal process can usemethods applied in semiconductor processes. However, since the magneticmaterial is hard to be etched unlike a general semiconductor material,it is difficult to use normal reactive ion etching (RIE) used in asemiconductor process. Instead, therefore, a physical etching methodsuch as ion milling, in which field-accelerated ions sputter on a samplesurface, has been used.

FIGS. 1A to 1E show a conventional method for manufacturing a patternedmedium using ion beam milling. That is, as shown in FIG. 1A, aferromagnetic material layer 520 containing Fe, Co, Ni or the like isfirst formed on a substrate 510 of Si or the like by using a sputteringmethod or the like. Then, on this ferromagnetic material layer 520, aresist pattern 530 corresponding to a desired pattern is formed byelectron beam writing. Further, as shown in FIG. 1B, ion beam milling iscarried out by using this resist pattern 530 as a mask, and an exposedportion of the ferromagnetic material layer 520 is subjected to etching.Then, as shown in FIG. 1C, a remaining resist film is removed. As shownin FIG. 1D, a nonmagnetic material layer 540 is coated to fill groovesformed by the ion milling. Lastly, by subjecting the substrate surfaceto chemical mechanical polishing (CMP), a patterned medium shown in FIG.1E is obtained.

However, in the above-described conventional manufacturing method, sincethe ferromagnetic material layer 520 is fabricated using the ion beammilling, damage remains on a crystal structure of the fabricatedsurface. Thus, fabrication with no damage is desired to further improvemagnetic properties.

In addition, as the etching by the ion milling is physical, there isalmost no difference in etching rates due to a difference betweenmaterials to be etched. As the ferromagnetic material layer 520 and theresist pattern 530 are scraped at approximately the same rate, an aspectratio of a shape that can be fabricated depends on a thickness of theresist pattern 530 as a mask. If there is about 20 nm difference inlevel between a surface of the resist pattern and the ferromagneticmaterial layer, a depth of 20 nm is a limit for a ferromagnetic materialto be etched. Thus, to carry out fabrication of a good aspect ratio, athin resist cannot be used.

In the case of the high recording density HDD, a surface of the magneticrecording medium must be smooth to reduce spacing between the magneticrecording medium and the magnetic head. Accordingly, as shown in FIG.1E, the nonmagnetic material layer 540 is buried in concave portions ofthe etched ferromagnetic material layer 520, and then the substratesurface must be smoothed in a CMP step. This CMP step imposes a load onthe process for forming the patterned medium.

On the other hand, a medium of a discrete tracking system (IEEETransactions on Magnetics Vol. 25, No. 5, P3381, 1989) has recently beenproposed as one type of a patterned medium. This patterned medium has amagnetic layer formed only in a track region. The magnetic layer isformed in a region between tracks using ion milling or the like.However, there is a level difference of 20 to 50 nm attributable topresence/non-presence of a magnetic layer on the medium surface, and thelevel difference causes a problem of considerably reducing seekingdurability.

In order to solve the problem of the level difference on the mediumsurface, a medium of a discrete system has been proposed, in which amagnetic layer that needs to become a region between tracks is madenonmagnetic by implanting nitrogen ions or oxygen ions therein (JapanesePatent Laid-Open No. 5-205257(published in 1993)).

In addition, as a method for forming a patterned medium having asmoother surface, a method has been proposed for forming a patternedmedium by selectively oxidizing a medium surface using a mask (U.S. Pat.No. 6,168,845).

In the above-described method of implanting oxygen ions or method ofpartially oxidizing the surface, since no etching steps are employed,the problem concerning the level difference on the surface due to ionmilling does not occur. However, these methods cannot completely removethe level difference on the medium surface. This is because a volume ofthe oxidized region made nonmagnetic is increased, and the mediumsurface of the oxidized region is raised.

In the case of using oxidation reaction, since a mask material havinghigh resistance to oxidation should preferably be used, a normal resistremoving step such as an O₂ ashing process cannot be used to remove themask material. Consequently, the removing the mask material brings aprocess load.

Also, regarding the manufacturing of MRAM, necessary films including alower ferromagnetic material layer, a tunnel oxide film layer, an upperferromagnetic material layer, and the like are formed on a substrate,and then these layers are physically etched using ion milling when eachmemory element region is plotted. However, short-circuiting may occurbetween the upper and lower ferromagnetic material layers because ofetching damage or etching residuals. Thus, it is desired to use amagnetic material patterning method having none of the above-describedproblems, high yields and good productivity.

On the other hand, the following problems exist concerning writing inthe servo region formed in the magnetic recording medium. First, when anormal sample servo (sector servo) system is used, a step of writingservo information by using a conventional servo writer is necessary.Since head movement is controlled and the servo information issequentially recorded in the respective servo regions of all tracks seton the magnetic recording medium, the step of writing servo trackinginformation is one of the steps that takes long time in themanufacturing process. In the future, a greater quantity of servoinformation will be necessary when a recording density is increased,requiring much longer time for the writing of the servo information bythe servo writer. Thus, in order to mass-produce high recording densityHDD devices inexpensively, it is required to shorten the time requiredfor the step of writing servo information.

Furthermore, even in the case of the magnetic recording medium using thedeep layer servo system, a step of forming a deep layer servo region isnecessary in addition to the step of forming the magnetic recordingmedium. In the case of the deep layer servo system, especially, sincewriting of the servo information is carried out on the full surface, atime load for the writing is extremely large, and thus a request forshortening the time is stronger than that for the sample servo system.

Therefore, also for the writing of the servo information, instead of themethod using the conventional servo track writer, it is desired toemploy a magnetic material patterning method having high productivityand capable of writing servo information in the magnetic recordingmedium all at once.

BRIEF SUMMARY OF THE INVENTION

An object of the present invention is to provide a magnetic materialpatterning method applicable to manufacturing of various magneticproducts, which causes no physical damage and has high productivity.

In order to achieve the above-described object, a first aspect of thepresent invention provides a method of patterning magnetic materialincluding preparing a ferromagnetic material layer containing at leastone element selected from the group consisting of Fe, Co and Ni,selectively masking a surface of the ferromagnetic material layer,exposing an exposed portion of the surface of the ferromagnetic materiallayer in halogen-containing active reaction gas or reaction liquid andconverting the exposed portion and a lower layer thereof into a compoundwith a component in the reaction gas or the reaction liquid by chemicalreaction to make the compound nonferromagnetic.

Here, “to make nonferromagnetic” means to lessen ferromagneticcharacteristics, and specifically means to convert a ferromagneticmaterial into a nonmagnetic or paramagnetic material.

According to the first aspect invention, since the nonferromagneticmaterial layer is selectively formed by the chemical reaction betweenhalogen and the ferromagnetic material layer, a magnetic patterncomposed of ferromagnetic and nonferromagnetic material layers can beformed. Because of the use of the chemical reaction, no physical damageis incurred, and also a large region can be patterned in a batchprocess. The halogenated nonferromagnetic material region has littlevolume expansion different from the case of oxidation, and thus anextremely smooth surface can be obtained without a step of polishing thesurface. Moreover, because of the use of halogenation reaction, ageneral resist can be used, and oxygen ashing process can be used forremoving the resist. By using this magnetic material patterning, it ispossible to manufacture patterned medium, to write servo information ina magnetic recording medium all at once, and to manufacture variousmagnetic products including a magnetic recording element such as anMRAM, and the like.

A second aspect of the present invention provides a magnetic recordingmedium including a plurality of recording regions made of ferromagneticmaterials, each containing at least one element selected from the groupconsisting of Fe, Co and Ni, and a nonferromagnetic material region forseparating the recording regions from each other, the region being acompound of the foregoing ferromagnetic material and halogen.

According to the second aspect, a patterned medium is provided by therecording region made of the ferromagnetic material and thenonferromagnetic material region made of the halogen compound of thisferromagnetic material. Since this nonferromagnetic material region isformed by the chemical method, the recording region is not damaged.Accordingly, manufacturing conditions cause no deterioration of magneticproperties, and good magnetic properties can be obtained. In addition,the surface of the nonferromagnetic material region and the recordingregion is not uneven, and a magnetic recording medium having highsubstrate smoothness can be provided.

A third aspect of the present invention provides a magnetic recordingmedium including a plurality of recording regions made of ferromagneticmaterials, each containing at least one element selected from the groupconsisting of Fe, Co and Ni, and a servo layer for separating therecording regions from each other, the servo layer having anonferromagnetic material region which is a compound of the foregoingferromagnetic material and halogen.

According to the third aspect, since servo information to be written inthe servo 11 layer of the magnetic recording medium is written based ona pattern of presence/non-presence of a halogen compound layer which canbe formed by chemical reaction. Therefore the servo information can bewritten in a large area all at once. Moreover, if the servo informationis written based on the presence/non-presence of the halogen compoundlayer, since volume expansion of the halogen compound layer is verysmall, a magnetic recording medium having excellent smoothness of asubstrate surface can be provided.

A fourth aspect of the present invention provides a magnetic randomaccess memory including; a lower electrode layer formed on a surface ofa substrate; a first ferromagnetic material layer made of a firstferromagnetic material containing at least one element selected from thegroup consisting of Fe, Co and Ni, the first ferromagnetic materiallayer being formed on the foregoing lower electrode layer; a tunnelinsulating layer formed on the first ferromagnetic material layer; asecond ferromagnetic material layer made of a second ferromagneticmaterial containing at least one element selected from the groupconsisting of Fe, Co and Ni, the second ferromagnetic material layerbeing formed on the tunnel insulating layer; and an insulating layersurrounding the foregoing first ferromagnetic material layer, tunnelinsulating layer, and second ferromagnetic material layer, andcontaining a compound layer of the foregoing first ferromagneticmaterial and halogen, and a compound layer of the second ferromagneticmaterial layer and halogen.

According to the fourth aspect, the insulating layer surrounding thefirst ferromagnetic material layer, the tunnel insulating layer, and thesecond ferromagnetic material layer is formed of a halogen compoundlayer. Therefore element formation can be carried out by employing amagnetic material patterning method using halogenation reactionaccompanied with no etching. Thus, no leakage due to etching isincurred, and an MRAM having high integration can be provided in alarge-area batch process.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1E are process views showing a conventional patterned mediumfabrication method using ion milling.

FIGS. 2A and 2B are partial plan and perspective views showing patternedmedia according to a first embodiment of the present invention.

FIGS. 3A to 3C are process views showing a manufacturing method of thepatterned medium of the first embodiment of the present invention.

FIGS. 4A and 4B are views showing VSM data regarding a ferromagneticmaterial layer and a nonferromagnetic material layer according to anexample 1 of the first embodiment of the present invention.

FIGS. 5A and 5B are views showing a pattern of a resist mask accordingto an example 2 of the first embodiment of the present invention, andshowing an electrophotograph of MFM image regarding an actually obtainedpatterned medium.

FIG. 6 is a sectional view showing a structure of a patterned mediumusing a multilayer film according to a second embodiment of the presentinvention.

FIGS. 7A and 7B are plan views showing pattern examples of servoinformation.

FIG. 8 is a plan view showing a pattern example of a magnetic recordingmedium surface of a continuous servo system.

FIG. 9 is a sectional view showing a structure of a magnetic recordingmedium having a deep layer servo structure according to a fourthembodiment of the present invention.

FIGS. 10A to 10E are process views showing a manufacturing method of themagnetic recording medium having the deep layer servo structure of thefourth embodiment of the present invention.

FIG. 11 is a device perspective view showing a structure example of ahard disk drive according to a fifth embodiment of the presentinvention.

FIG. 12 is a device perspective view showing a structure of another harddisk drive according to the fifth embodiment of the present invention.

FIGS. 13A to 13C are process views showing a manufacturing method of aMRAM according to a sixth embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Description will be made of the embodiments of the present inventionwith reference to the accompanying drawings.

FIRST EMBODIMENT

FIG. 2A is a partial plan view showing a structure of a magneticrecording medium according to a first embodiment of the presentinvention; and FIG. 2B is a perspective view of the same.

The magnetic recording medium of the first embodiment of the presentinvention is a so-called patterned medium. As shown in FIGS. 2A and 2B,this magnetic recording medium includes a recording layer 20 on asubstrate 10. The recording layer 20 includes a ferromagnetic materialregion 20A and a nonferromagnetic material region 40. The ferromagneticmaterial region 20A contains any of Fe, Co and Ni, and has dottedexposed portions. The nonferromagnetic material region 40 surrounds atleast an upper layer portion of the ferromagnetic material region 20A.Substantial recording regions are separated from each other by thenonferromagnetic material region 40. Here, the nonferromagnetic regionmeans a region having lost magnetism at least as a ferromagneticmaterial, and exhibiting nonmagnetic, diamagnetic or paramagneticproperties.

The nonferromagnetic material region 40 is obtained by makingnonferromagnetic using chemically reacting a layer containing the samecomponent as that of the ferromagnetic material region 20A with activereaction gas. The composition of the nonferromagnetic material region 40is common to that of the ferromagnetic material region 20A, i.e.containing one of Fe, Co and Ni.

According to such a magnetic recording medium of the first embodiment,since an etching step such as ion milling needed in the conventionalpatterned medium fabrication process is not necessary, and a CMP stepcan be omitted, it is possible to greatly simplify a process. Moreover,since damage accompanied by the step of ion milling or the like can beeliminated, it is possible to improve magnetic properties.

Next, the structure of the magnetic recording medium of the firstembodiment and its manufacturing method will be described more indetail.

As shown in FIG. 2A, the ferromagnetic material regions 20A areregularly disposed at constant intervals on the surface of the magneticrecording medium, and the nonferromagnetic material region 40 is formedto surround the ferromagnetic material regions. Each ferromagneticmaterial region 20A constitutes 1 recording bit as a recording unit.Preferably, each ferromagnetic material region 20A should be completelyindependent. However, as shown in FIG. 2B, it is satisfactory that atleast an upper layer portion of the ferromagnetic material region 20A issurrounded by the nonferromagnetic material region 40. Accordingly,recording regions are substantially separated from each other. Theferromagnetic material regions 20A should be set to 100 nm square orsmaller, preferably 80 nm square or smaller, in such a manner as to seta single magnetic domain state where respective directions ofmagnetization thereof are aligned in one direction. The shape of theferromagnetic material regions 20A are not limited to a rectangle, butvarious shapes can be employed, for example, a circle, an ellipticalshape and the like.

For a recording system of the ferromagnetic material region 20A, bothlongitudinal and perpendicular recording systems can be employed. Toachieve a high recording density, however, the perpendicular recordingsystem is preferable.

The ferromagnetic material region 20A contains one of the elements Fe,Ni and Co, which are ferromagnetic materials, in its composition. Forexample, the ferromagnetic material region is composed of a crystalmaterial of Ni—Fe or Fe—Al—Si: a Co-base amorphous material of Co—Zr—Nb;an Fe-containing microcrystal material of Fe—Ta—N; Fe; Co; Fe—Co; Co—Cr;Ba ferrite; and the like. Among these, preferably, alloy of CoPt,CoCrPt, FeCo, FePd, FePt or the like having large perpendicular magneticanisotropy, or a material such as Co/Pd, or Co/Pt multiplayer filmshould be used for formation of the ferromagnetic material region.

The nonferromagnetic material region 40 is obtained by halogenating alayer having an identical composition to that of the above-describedferromagnetic material region 20A. For example, as halogenatedmaterials, CoF₂, CoF₃, FeF₂, FeF₃, and NiF₂ can be cited. These are allantiferromagnetic materials, but exhibit paramagnetism at roomtemperature except for CoF₃ and FeF₃, because of low Neel temperature(Tn).

FIGS. 3A to 3C are process views showing a manufacturing method of themagnetic recording medium of the embodiment.

First, as shown in FIG. 3A, a ferromagnetic material layer 20 is formedin a film thickness of, for example about 10 nm to 50 nm, on a substrate10 of Si or the like by a sputtering method or the like. Then, resist 30is coated on the ferromagnetic material layer 20 by a spin coater or thelike. There is no particular limitation on a film thickness of theresist 30. The resist 30 may have a thickness to cover a surface of theferromagnetic material layer 20 without any pinholes. The resist 30 isselectively exposed by using EB writing system or the like, and througha developing step, a resist pattern corresponding to a plane pattern ofFIG. 2A is formed. That is, a surface of a portion to be left as theferromagnetic material region is covered with the resist 30, and otherportions are exposed. Then, the substrate obtained after the resistpatterning are exposed to active reaction gas containing halogen.

For the reaction gas containing halogen, for example, gas such as CF₄,CHF₃, CH₂F₂, C₂F₆, C₄F₈, SF₆, Cl₂, CCl₂F₂, CF₃I or C₂F₄ can be used.

The active reaction gas is preferably active radical. Various methodsare available for generating radicals. For example, a existing plasmaCVD apparatus or a dry etching apparatus can be used. When reaction gasis introduced into a chamber of such an apparatus and a high-frequencyvoltage is applied, field-accelerated electrons collide with thereaction gas, the reaction gas is separated and radicals, which arechemically extremely active, are generated. A substrate temperature maybe set at normal temperature; however, to increase a reaction speedmore, heating may be applied within a range not affecting magnetism ofthe ferromagnetic material region.

A suitable example of a plasma generation apparatus is, for example, aninductive coupled plasma (ICP) apparatus. The ICP apparatus includes aPlaten RF having a function of inducting plasma to the substrate side,which is provided separately from a Coil RF mainly having a function ofgenerating plasma. These portions can be separately set for outputthereof. For example, by setting the Coil RF to 300 W and the Platen RFto 0 W, high density plasma, which is suitable for producing radicalreaction, is generated. An effect of sputtering can be suppressed to aminimum since no damage is given to the medium surface. To preventsputtering the medium surface, a pressure in a reaction chamber shouldbe set slightly high, e.g., 10 to 30 mtorr, more preferably about 20mtorr. In the case of using CF₄ as reaction gas, a gas flow rate shouldbe set in a range of 10 to 50 sccm, preferably about 20 sccm.

For example, as shown in FIG. 3A, when the ferromagnetic material layer20 not covered with the resist 30 is exposed to active fluorine (F)radicals generated from CF₄ gas, the exposed surface of theferromagnetic material layer 20 is gradually halogenated in a depthdirection by the F radicals.

Thus, as shown in FIG. 3B, the halogenated region becomes a halidelayer, and becomes a nonferromagnetic material region 40 which has lostmagnetism. On the other hand, the region having its surface covered withthe resist 30 becomes a ferromagnetic material region 20A. A depth ofthe nonferromagnetic material region 40 should preferably be setapproximately equal to a depth of the ferromagnetic material layer 20.However, such equality of depth is not always necessary, and withrespect to a thickness of the ferromagnetic material layer 20, forexample, the depth of the nonferromagnetic material region 40 is set to½ of the ferromagnetic material layer 20 or more, more preferably ⅔thereof or more.

Note that a dry process is not always necessary, and a similar resultcan be obtained by a wet process. For example, CoCl₃ or the like may behalogenated by using a HCl solution.

Lastly, by removing the remaining resist 30, a patterned medium shown ineach of FIG. 3C and FIGS. 2A and 2B can be obtained. For the removal ofthe resist, ashing process using oxygen plasma can be employed.

According to the manufacturing method of the above-described firstembodiment, it is possible to obtain a patterned medium in which therecording region of the ferromagnetic material layer 20A is surroundedwith the nonferromagnetic material region 40 which is halogenated metal.For example, since Neel temperatures (Tn) of CoF2 and NiF2 which are thenonferromagnetic material region 40 obtained by halogenation reactionare very low, respectively 38K and 73K. Thus, as CoF2 and NiF2 surelyexhibit paramagnetism at room temperature, no mutual magnetic operationoccurs between adjacent recording bits, and adjacent magnetic recordingis isolated. Therefore, this manufacturing method using halogenationreaction is suitable for manufacturing the patterned medium.

On the other hand, for CoO and NiO obtained by oxidation reaction, whichare the nonferromagnetic material regions of the discrete medium and thepatterned medium disclosed in Japanese Patent Laid-Open No. 5-205157(published in 1993) and U.S. Pat. No. 6,169,845 already described above,magnetic phase transition temperatures (Tn) are respectively 291K and548K. Thus, oxidized metal generated by oxidation reaction exhibitsantiferromagnetism at room temperature. In the case of a mediumincluding a ferromagnetic material buried in a diamagnetic material, aferromagnetic material layer is magnetically not completely isolated,and thus magnetic recording of an adjacent recording bit may beadversely affected. For example, when identical signals are recorded inadjacent bits, there is a high possibility that magnetization reversalwill extinguish a stored content.

Therefore, the patterned medium having the nonmagnetic material regionobtained by the halogenation reaction according to the first embodimentcan acquire better magnetic properties compared with the patternedmedium having the nonmagnetic material region obtained by the oxidationreaction.

Generally, since a halide, especially a fluoride has strong ioncrystallization as represented by CaF₂ (fluorite), it is easy to obtaina crystal of good orientation. The crystal is unlikely to be dissolvedin water, and is chemically stable. When a fluoride and an oxide of thesame metal are compared with each other, bond dissociation energy (D) ofthe fluoride is generally larger. For example, D of MgF₂ is 511.7kJ/mol, and D of MgO is 336.8 kJ/mol. Thus, the fluoride can be expectedto exhibit higher stability than the oxide.

Moreover, the good orientation of the fluoride may realize a uniformparticle size of the adjacent ferromagnetic material regions 20A, andthus an effect of more improvement in the magnetic properties of theferromagnetic material region can be expected.

In addition, CoO which is an oxide is tetragonal where a latticeconstant of a c axis is 4.124. However, since a lattice constant of a caxis of a fluoride CoF₂ is small, i.e., 3.180, there is almost littlevolume expansion such as that in the oxidation reaction occurs.Therefore, unevenness due to the presence of a halogenated region doesnot generated, providing extremely good smoothness.

According to the manufacturing method of the above-described firstembodiment, since the surface of the ferromagnetic material layer 20 isnot etched, surface heights of the nonferromagnetic material region 40and the ferromagnetic material region 20A are approximately equal toeach other, making it possible to approximately maintain smooth surfacesof reaction starting time. Thus, unlike the conventional case offabricating a patterned medium by using ion milling, a step of smoothinga surface by CMP is not necessary in the last step of the process.Therefore, it is possible to greatly shorten the manufacturing process.

In addition, in the case of using ion milling, an influence of damagecaused by the ion milling remains in a fabricated surface layer of theferromagnetic material region, for example its sidewall. However,according to the method of the above-described first embodiment, theferromagnetic material region 20A is not damaged. Thus, characteristicdeterioration caused by the process is unlikely to occur in theferromagnetic material region 20A.

Moreover, in the above-described conventional patterning method usingthe oxidation reaction, since metal such as Ti having high resistance tooxidation or an inorganic film such as SiO₂ is mainly used as a mask, aRIE process must be executed to remove such a mask after oxidationreaction. During this RIE process, the medium surface may be partiallydamaged by sputtering. On the other hand, in the method of patterning amagnetic material according to the first embodiment, since thehalogenation reaction is used, a general resist mask can be used. Theresist can be easily removed by oxygen ashing process which can reducethe damage to the medium surface to a minimum.

Moreover, according to the manufacturing method of the above-describedfirst embodiment, because the shape of the ferromagnetic material region20A is not dependent on a resist film thickness, the resist filmthickness can be reduced. Thus, for example, it is possible to use athin resist pattern having a dot thickness of about 20 nm utilizing aself-organization phenomenon (phase separation phenomenon) of a diblockcopolymer. A block copolymer means a copolymer composed of a linearpolymer including a plurality of homopolymers as constituent components.Especially one obtained by chemically coupling two kinds of polymers iscalled a diblock copolymer. For example, for such a resist material, adiblock copolymer composed of polystyrene (PS) and polymethylmethacrylate (PMMA) generally used for an optical disk substrate or thelike can be used.

By controlling a composition ratio and a molecular weight of the blockcopolymer, various structures can be easily formed. For example, when asolution in which polystyrene (PS) and polymethyl methacrylate (PMMA)are mixed is coated on the ferromagnetic material layer 20, a sea-island(Sphore) structure can be obtained, which is phase-separated into an“island” region of PMMA and a “sea” region of PS. By exposing thissea-island structure to ozone and by selectively vaporizing PMMAtherein, dot patterns each having a regular PMMA thickness of 20 nm anda diameter less than 40 nm can be obtained. That is, dot patterns of asize suited for formation of a patterned medium can be formed all atonce.

In the conventional method of using the ion beam milling, use of theabove-described thin resist is difficult. However, according to themethod of the first embodiment using the chemical method, such thinresist can be used as an etching mask. If patterned resist is obtainedby utilizing the self-organization phenomenon of the diblock copolymer,the patterning of the resist by EB writing system which takes long timeis made unnecessary. Thus, the method of the embodiment becomes veryeffective means for simplifying the process.

As described above, according to the magnetic recording medium of thefirst embodiment, in addition to excellent resistance to thermalfluctuation and the effect of preventing crosstalk and partial erasingfrom an adjacent bit, which the patterned medium structure itself has,it is possible to improve magnetic properties by reducing damagereceived in the manufacturing process, and to shorten the process.

Hereinafter, description will be made for examples of examination thatthe inventors made in order to verify the effect of the patterned mediumof the first embodiment.

EXAMPLE 1

First, CoPt was deposited by 20 nm on a Si substrate by a sputteringmethod, and a magnetic force microscope (MFM) image on a surface of thissample was observed. An image of a perpendicular magnetic recordingmedium having a high-contrast maze pattern which is a typicalferromagnetic pattern was observed. A hysteresis curve in aperpendicular direction was measured by a vibrating sample magnetometer(VSM), and a curve, as shown in FIG. 4A, which has a squareness ratio of0.49 and a coercive force of 1500 Oe was obtained.

Then, a composition of the sample surface was analyzed by using X-rayphotoelectron spectroscopy (XPS). A peak inherent in Co was observed atbinding energy=778 eV. A peak (781 eV) of CoO was simultaneouslyobserved; however, this peak was due to natural oxidation of oxygen inthe atmosphere. Two peaks inherent in Pt were also observed within therange from 70 to 75 eV.

Subsequently, CoPt was deposited by 20 nm on the Si substrate by thesputtering method. This sample was placed in a sealed chamber, plasmawas generated in the chamber, and CF4 gas was introduced to generate Fradicals. Then, a surface of the sample was exposed to the F radicalsfor about 30 seconds. A sample temperature in this event was set to roomtemperature.

Then, when a composition of the sample surface was analyzed by usingXPS, both peaks 778 eV (Co) and 781 eV (CoO) disappeared, and a new peak(cobalt fluoride) of 783 eV was observed. No peak shifting was observedat a Pt peak. This shows that exposure to the F radicals surelyconverted the surface into cobalt fluoride.

In addition, when the composition of the sample surface was analyzed byusing scanning Auger electron spectroscopy (AES), conversion of CoPtinto cobalt fluoride was verified. By observing changes of peaks of thecobalt fluoride with passage of time while sputtering, it was found outthat the cobalt fluoride existed from a medium surface to a depth ofabout 10 nm. It was also verified that it was possible to covert all 20nm which is a thickness of CoPt into a halide by extending the exposuretime of the F radicals.

When a MFM image of the sample surface was also observed, a typical MFMimage seen when magnetization disappeared was observed.

By observing this sample with VSM, data of a typical paramagneticmaterial as shown in FIG. 4B was obtained. This is attributed to thefact that CoF₂ is originally an antiferromagnetic material, but behaveslike a paramagnetic material at room temperature because of an extremelylow Neel temperature.

As a result, it was verified that the CoPt film which is a ferromagneticmaterial layer was converted into a halide within a short time by beingexposed to the F radicals, and that magnetism thereof disappeared.

EXAMPLE 2

A patterned medium sample, in which ferromagnetic material CoPt regionsare surrounded by antiferromagnetic material CoF₂, was prepared. Thatis, first, CoPt was deposited by 20 nm on a Si substrate by a sputteringmethod. Then, resist was coated in a thickness of about 1.0 μm on thisCoPt film by spin coating, and a resist pattern as shown in FIG. 5A wasformed after batch exposure and development. In this example, a size ofeach ferromagnetic material region on a surface layer was set to 2.0 μmsquare.

A surface of this sample was exposed in F radicals generated underconditions similar to those of the example 1 for about 30 seconds whilebeing maintained at room temperature. Then, the resist was removed byusing an oxygen ashing apparatus.

When a MFM image of this sample was observed, a magnetic patternequivalent to a resist pattern as shown in FIG. 5B was obtained. Thatis, regarding a region covered with a resist film., a MFM image of aferromagnetic material having typical perpendicular magnetic anisotropywas observed. In a region where a CoPt surface was exposed, a typicalMFM image seen when magnetization disappeared was observed.

Moreover, when the region where the CoPt surface was exposed wasanalyzed by using XPS, conversion of CoPt into a halide was verified.Identification of a composition was carried out by using XPS, however,verification can be carried out by using a surface analyzer such as AESor secondary ionization mass spectrometry (SIMS).

The sample thus obtained was a uniformly continuous thin film having nounevenness on its surface. In addition, magnetically, as shown in FIG.2A or FIG. 2B, the sample was verified to be a patterned medium whereferromagnetic material regions 20A isolated at least on a surface layerwere regularly arrayed in a nonferromagnetic material region 40.

EXAMPLE 3

In order to form finer patterns of the ferromagnetic material regionthan that of the above-described example 2, electron beam (EB) writingwas carried out in exposure of resist. Accordingly, fine ferromagneticmaterial region patterns of about 80 nm square were formed. Otherconditions were the same as those of the above example 2, and by usingthese conditions, a sample was prepared. That is, CoPt was deposited by20 nm on a Si substrate by sputtering. Then, nega-resist was coatedthereon, a minute resist pattern was formed by EB writing, and exposurethereof in F radicals was carried out for about 30 seconds at roomtemperature. Thereafter, the resist was removed.

An obtained sample was observed by MFM, and a single color image wasobtained in a ferromagnetic material region. That is, it was verifiedthat by reducing the ferromagnetic material region to a size of about 80nm square, a single magnetic domain state was set in this region. Whenmagnetic properties in a perpendicular direction were observed by VSM, asquareness ratio of 1.00 and a coercive force of 4500 Oe were obtained.These values represent a squareness ratio twice as large and a coerciveforce three times as large compared with the VSM curve of the CoPt filmnot exposed in the F radicals after sputtering in the example 1, andimprovement in the magnetic properties was observed. It was alsoverified that in a comparative example 1 to be described later, bettermagnetic properties were obtained compared with a patterned medium of anequal size fabricated by the conventional method.

EXAMPLE 4

CoPt was deposited by 30 nm on a Si substrate by sputtering. Then, theresultant structure was left under oxygen atmosphere for one day tooxidize a CoPt surface. When the surface was observed by XPS, a peak(781 eV) of CoO was verified.

Subsequently, resist was coated in a thickness of about 1.0 μm on theCoPt film by spin coating, and after batch exposure and development, aplurality of rectangular resist patterns of 2.0 μm square as shown inFIG. 5A were formed.

A surface of this sample was exposed in F radicals generated undersimilar conditions to those of the example 1 for about 30 seconds whilebeing maintained at room temperature. Then, the resist was removed byusing an oxygen ashing apparatus.

When a MFM image of this sample was observed, a magnetic patternequivalent to a resist pattern as shown in FIG. 5B was obtained. Thatis, regarding a region covered with the resist film, a MFM image of aferromagnetic material having typical perpendicular magnetic anisotropywas observed. In a region where a CoPt surface was exopsed, a typicalMFM image seen when magnetization disappeared was observed. In asimultaneously observed surface leveling image (similar to AFM surfacetopological image), almost unevenness is not observed.

In addition, the region where the CoPt surface was exposed was analyzedby using XPS, conversion of CoPt into a halide was verified.

As a result, it was found out that even when a reacting surface wasnaturally oxidized beforehand, a halide layer could be obtained by latersubstitution reaction of a fluorine radical. It was also verified thatthis method enabled formation of a patterned medium having almost flatmedium surface.

COMPARATIVE EXAMPLE 1

As a comparative example, a sample was prepared according to aconventional manufacturing method of a general patterned medium. Thatis, CoPt was deposited by 20 nm on a Si substrate by a sputteringmethod. Then, nega-resist was coated on a surface thereof, and by EBwriting, a pattern equivalent to a ferromagnetic material region of 80nm square was formed similarly to the example 3. Subsequently, a surfaceof the sample was uniformly etched by Ar ion beam milling. When CoPt ofa region not covered with the resist was etched by about 20 nm, theremaining resist was removed by O₂ ashing. Then, SiO₂ was deposited by20 nm by sputtering, and the surface was covered so as to fill a CoPtgroove portion formed by ion milling. In addition, the surface waspolished by CMP processing. Accordingly, a patterned medium in whichCoPt ferromagnetic material regions of about 80 nm square, which areindependent of one another, are surrounded with SiO₂ was obtained. Thatis, the prepared sample was equivalent to one where the halide portionof the sample prepared in the example 3 was changed to SiO₂.

When a CoPt portion was observed by MFM, an image was approximately thesame as the magnetic image of the example 2 having the size of theferromagnetic material region set to 2 μm square. When magneticproperties in a perpendicular direction were observed by VSM, asquareness ratio of 0.70 and a coercive force of 2000 Oe were obtained.These values represented improvement in magnetic properties comparedwith those of the CoPt continuous film not exposed to the F radicalsimmediately after sputtering in the example 1. However, compared withthe patterned medium having the ferromagnetic material region of thesame size as the example 3, the magnetic properties were inferior.

(Result)

By comparing the comparative example with the example 3, it was verifiedthat the manufacturing process of the patterned medium of the example 3was not only simple, but also the magnetic properties of theferromagnetic material region thereof were improved compared with thoseof the patterned medium of the comparative example.

One of the reasons may be as follows. That is, in the case of the sampleof the comparative example, since fabrication is carried out by usingthe ion beam milling, the fabricated surface of the ferromagneticmaterial region was at least damaged. On the other hand, in the case ofthe sample of the example 3, since the chemical method accompanied withno physical damage is used, there is no damage on the surface of theferromagnetic material.

In addition, in the case of the patterned medium of the example 3, CoPtis converted into a halide to form the nonferromagnetic material region.However, the halide is an ionic crystal, and is not amorphous such asSiO₂ forming the nonferromagnetic material region of the patternedmedium of the comparative example. Thus, it can be conceived that goodorientation of the ionic crystal realizes a uniform CoPt particle sizeof the adjacent ferromagnetic material regions, improving magneticproperties more.

Moreover, from the result of the example 4, it was verified that whenhalogenation reaction was used for formation of the nonmagnetic materialregion, surface smoothness required for the HDD medium, i.e., adifference in level of 0.8 nm or lower, was sufficiently obtained.

SECOND EMBODIMENT

FIG. 6 is a sectional view showing a structure of a patterned mediumaccording to a second embodiment.

Also in the patterned medium of the second embodiment, a method forforming a nonferromagnetic material region uses the similar chemicalmethod as that described in the first embodiment. A difference from thefirst embodiment is that a multilayer film is formed instead of theferromagnetic material thin film formed on the Si substrate. Themultilayer film includes a plurality of layers, e.g., ferromagnetic andmetal layers, alternately laminated in a regular manner. For example, amultilayer film obtained by alternately laminating Co and Pt or Co andPd is known. By using such a multilayer film a high coercive force canbe obtained. Other constitutions and manufacturing methods are common tothose of the first embodiment.

In order to form the patterned medium of the second embodiment, first,as shown in FIG. 6, a multilayer film 21 alternately laminating Colayers 21 a and Pt layers 21 b is formed on a substrate 10 by asputtering method or the like. For example, a film thickness of the Colayer 21 a should be set in a range from 0.2 nm to 1.0 nm, preferably0.5 nm. A film thickness of the Pt layer 21 b should be set in a rangefrom 0.5 nm to 2.0 nm, preferably 1.0 to 2.0 nm. The number of therespective layers is about 10; the number of the Pt layers is largerthan that of the Co layers by one layer.

The process thereafter is basically similar to that of the firstembodiment. Resist is coated on the multilayer film 21, the resist isselectively exposed by using EB writing or the like and is developed,then a resist pattern equivalent to a portion to be left as aferromagnetic material region is formed. Subsequently, a surface of themultilayer film 21 having the resist pattern formed thereon is exposedin active reaction gas or in a reaction liquid.

For example, when the surface of the multilayer film 21 having theresist pattern formed thereon is exposed to F radicals, the F radicalshalogenate the exposed surface of the multilayer film 21 to form ahalide region 25.

For an artificial lattice, a regularly laminated structure, especiallyits interface, is important. Accordingly, if even one layer of thelaminated structure is physically damaged or a chemical compositionthereof is changed, magnetism in upper and lower laminated portions islost. Thus, as shown in FIG. 6, the halide region 25 may be formed onlyon a limited surface layer film of the multilayer film 21.

Thereafter, by removing the remaining resist, as in the case shown inFIG. 2A, a patterned medium including a ferromagnetic material region20A made of the multilayer film and a nonferromagnetic material region40 surrounding the ferromagnetic material region 20A can be obtained.

As described above, in the conventional method using the ion beammilling, since the fabricated surface of the ferromagnetic materialregion is damaged, it is difficult to form a patterned medium using amultiplayer film, in which even small damage affects magneticproperties. However, by using the method of the second embodiment, thepatterned medium using the multilayer film can be fabricated easily.

Also in this case, as described above in the first embodiment, a thinresist film can be used. Thus, instead of resist patterning carried outby using EB writing, it is possible to use a resist patterning methodusing a self-organization phenomenon of a diblock copolymer.

Hereinafter, description will be made for examples of examination thatthe inventors made in order to verify an effect of the patterned mediumusing the multilayer film of the second embodiment.

EXAMPLE 5

First, Co films in a thickness of 4.4 nm and Pt films in a thickness of9.5 were alternately laminated to form ten layers on a Si substrate by asputtering method, thus forming a multilayer film In this state, MFM wasobserved, and a magnetic pattern inherent in a ferromagnetic materialhaving perpendicular magnetic anisotropy was identified. In addition,when magnetic properties in a perpendicular direction were observed byVSM, a squareness ratio of 0.8 and a coercive force of 2000 Oe wereobtained.

Subsequently, resist was coated in a thickness of 1.0 μm on themultilayer film and a fine ferromagnetic material region pattern ofabout 80 nm square was formed by EB writing. Under conditions similar tothose of the example 1, this multilayer film with the resist pattern wasexposed to F radicals for about 30 seconds at room temperature, and asurface of an exposed portion was halogenated. Then, the remainingresist was removed.

Observation was made for a MFM image of a sample thus obtained, andpresence of a ferromagnetic material region and a nonferromagneticmaterial region at a high contrast ratio was verified. This contrastratio was higher than that obtained in the example 3. For theferromagnetic material region, it was also verified that a single colorimage was formed, and a single magnetic domain was formed. For thisportion, magnetic properties in a perpendicular direction were observed,and a squareness ratio of 1.00 and a coercive force of 5000 Oe wereobtained.

It was thus verified that when a patterned medium using such amultilayer film was formed, an S/N ration higher than that in the caseof using a single CoPt layer film was obtained.

EXAMPLE 6

Under conditions similar to those of the example 5, a multilayer filmwas formed on a substrate. On the multilayer film a solution of PS-PMMAdiblock copolymer was coated, and a sea-island structure which isphase-separated into an “island” region of PS and a “sea” region of PMMAwas formed. This sea-island structure was exposed in ozone, PMMA wasselectively vaporized, and dot patterns of PS were formed in a thicknessof about 20 nm and a diameter of about 40 nm.

Subsequently, this sample was exposed to F radicals at room temperaturefor about 30 seconds, and a surface of the exposed portion washalogenated. Then, the remaining PS was removed.

A MFM image of the obtained sample was observed, and it was verifiedthat a region covered with PS formed a ferromagnetic material region ofa single magnetic domain, and regions other than the above region becamenonferromagnetic material regions.

As described above, it was verified that according to the method of theembodiment, it was possible to fabricate a patterned medium having afine ferromagnetic region by employing a resist pattern using theself-organization phenomenon of the diblock copolymer with a leveldifference of only 20 nm.

In other words, instead of EB writing which takes long time, by using apatterning method of resist using phase separation of a diblockcopolymer, it is possible to greatly shorten a resist patterningprocess.

THIRD EMBODIMENT

A third embodiment relates to writing of servo information in a servoregion on a magnetic recording medium. The magnetic material patterningmethod using the halogenation reaction described in the first embodimentcan be used not only for forming a patterned medium but also for writingservo information in the servo region all at once.

That is, in the magnetic recording medium of the third embodiment,resist is coated on a surface of a recording layer having aferromagnetic material layer formed thereon, and an opening patternequivalent to a servo signal pattern is formed in a portion to be aservo region. As the servo signal pattern, one generally used may beused. For example, formed is one as shown in FIG. 7A in which aplurality of wedge-shaped patterns 65 are arrayed, or one as shown inFIG. 7B in which patterns 66 alternately formed left and right arearrayed in two rows by being shifted up and down by half pitches.

After the resist pattern is formed, under conditions similar to those ofthe first embodiment, the magnetic recording medium is exposed in activereaction gas, for example F radicals. A ferromagnetic material layer ofthe opening portion of the resist pattern is halogenated to be changedto a nonferromagnetic material region. By removing the resist, amagnetic pattern equivalent to the resist pattern can be formed in theservo region on the magnetic recording medium.

As long as the magnetic pattern formed in the servo region can beverified as magnetic information, it is not a problem that which one ofinner and outer sides of the pattern should be set as a ferromagneticmaterial region or as a nonferromagnetic material region.

By using the above method to write the servo information, writingoperations in the respective regions can be carried out in a batchprocess. Thus, it is possible to greatly shorten time necessary forwriting of the servo information.

Moreover, the method of writing servo information according to the thirdembodiment can also be applied to writing servo information of amagnetic recording medium of a continuous servo system, which is capableof always taking out a servo signal in any position of a magnetic headon a disk. As the magnetic recording medium of the continuous servosystem, for example, a magnetic recording medium is disclosed inJapanese Patent Laid-Open No. 2000-19200 (published in 2000). Thismagnetic recording medium includes servo patterns located adjacently toboth sides of a recording track, which are formed on a full surface ofthe magnetic recording medium. In the Japanese Patent Laid-Open No.2000-19200, pre-formatting using a photolithography process and a thinfilm forming process is only disclosed, and specific servo patternforming method is not taught. However, by a method similar to thepatterned medium forming method of the first embodiment, a servo patternused for the continuous servo system can be formed.

FIG. 8 shows an example of a servo pattern formed in a medium of such acontinuous servo system. As shown in FIG. 8, servo patterns 81 areperiodically disposed in both sides of each recording track 82 where arecording region is formed, the patterns being shifted by a half period.A shape of the servo pattern 81 is not limited to a dot shown in thedrawing, but may be a rectangular or long-axis pattern.

The dot patterns 81 regularly disposed in both sides of the recordingtrack 82 can be patterned by using regular dot resist patterns formed byutilizing the above-described self-organization phenomenon (phaseseparation phenomenon) of the diblock copolymer. In such a case, sinceextremely fine patterns can be formed all at once on a full surface ofthe recording medium without using EB writing or the like, it ispossible to greatly simplify the process, facilitating the formation ofthe magnetic recording medium of the continuous servo system.

There is no particular limitation on the recording system and structureof the recording layer of the recording medium of the third embodiment.A recording layer of a normal longitudinal recording system, or arecoding layer of a perpendicular recording system may be employed. Inaddition, a continuous film of a single layer, an multilayer film or apatterned medium as described in each of the first and secondembodiments may be employed. When a patterned medium is formed, writingof servo information can be carried out simultaneously with theformation of the patterned medium.

Hereinafter, description will be made for examples of the thirdembodiment, which are made by the inventors.

EXAMPLE 7

A sample was prepared under conditions similar to those of the example2, except for formation of a resist pattern equivalent to thewedge-shaped opening pattern 65 shown in FIG. 7A. That is, CoPt wasdeposited by 20 nm on a Si substrate by a sputtering method. Then,resist was coated in a thickness of about 1.0 μm on the CoPt film byspin coating, and through batch exposure and development, a wedge-shapedopening pattern shown in FIG. 7A was formed. Subsequently, a surface ofthe sample was exposed in F radicals for about 30 seconds while beingmaintained at room temperature. Then, the resist was removed by using anoxygen ashing apparatus.

By XPS, it was verified that only CoPt of the opening portion of theresist exposed to the F radicals was chemically changed to anantiferromagnetic material (CoF₂). Also, when observation was made byMFM, a magnetic image of a wedge-shaped pattern equivalent to a resistpattern was obtained.

As a result, it was verified that by using the magnetic materialpatterning method of the third embodiment, it was possible to writeservo information, i.e., tracking servo information in a large area allat once.

EXAMPLE 8

A sample having the servo pattern 81, shown in FIG. 8, changed to arectangular shape was prepared. The sample was prepared under conditionssimilar to those of the example 2, except for formation of an openingpattern corresponding to the servo pattern, by using resist. That is,CoPt was deposited by 20 nm on a Si substrate by a sputtering method.Then, resist was coated in a thickness of about 1.0 μm on the CoPt filmby spin coating, and through batch exposure and development, arectangular opening pattern was formed. Subsequently, a surface of thesample was exposed in F radicals for about 30 seconds, while beingmaintained at room temperature. Then, the resist was removed by using anoxygen ashing apparatus.

By XPS, it was verified that only CoPt of the opening portion of theresist exposed to the F radicals was chemically changed to CoF₂. Also,when observation was made by MFM, a magnetic image of a rectangularpattern equivalent to the resist pattern was obtained.

As a result, is was verified that by using the magnetic materialpatterning method of the third embodiment, it was possible to writeservo information, i.e., tracking servo information in a large area allat once.

FOURTH EMBODIMENT

A fourth embodiment relates to a structure of a magnetic recordingmedium of a deep layer servo system, and a manufacturing method thereof.

FIG. 9 shows the structure of the magnetic recording medium that is thedeep layer servo system of the fourth embodiment.

A ferromagnetic material layer 64 is formed on a substrate 15, and anonferromagnetic material region 62 having a servo information patternis formed on a surface layer of the ferromagnetic material layer 64. Aservo layer 60 is composed of the ferromagnetic material layer 64 andthe nonferromagnetic material region 62. On the servo layer 60, aferromagnetic material layer 25 as a recording layer is formed with anonmagnetic material layer 70 interposed therebetween.

FIGS. 10A to 10E are process views showing the manufacturing method ofthe magnetic recording medium of the fourth embodiment.

A servo layer is basically formed by using the same chemical method asthat for the fabrication method of the patterned medium of the firstembodiment. That is, first, as shown in FIG. 10A, the ferromagneticmaterial layer 64 is formed on the substrate 15 by using a sputteringmethod or the like. For this ferromagnetic material layer 64, variousferromagnetic materials containing Co, Ni, Fe can be used similarly tothe case of the ferromagnetic material layer 20 of the first embodiment.Also, a multilayer film as described above in the second embodiment maybe formed.

Then, a resist film is coated on the ferromagnetic material layer 64,and through batch exposure and development, on the ferromagneticmaterial layer 64, a resist pattern 32 equivalent to servo informationis formed on a full surface of the substrate. There is no particularlimitation placed on the resist pattern 32, and for example, a generalservo information pattern as shown in FIG. 7A or FIG. 7B may be used.Then, under conditions similar to those of the first embodiment, asurface of the substrate is exposed to active reaction gas or reactionliquid, for example F radicals.

As shown in FIG. 10B, the ferromagnetic material layer 64 of a regionexposed to the F radicals loses magnetism to be changed to anonferromagnetic material region 62. The nonferromagnetic materialregion 62 needs not be so deep as long as a magnetic pattern as servoinformation can be formed.

As shown in FIG. 10C, after the remaining resist is removed, anonmagnetic layer 70 is formed on the substrate surface by using a CVDmethod or the like as shown in FIG. 10D. For this nonmagnetic layer 70,an oxide such as SiO₂, Al₂O₃ or TiO₂, a nitride such as Si₃N₄, AlN, TiNor BN, or carbide such as TiC may be used.

Further, as shown in FIG. 10E, a ferromagnetic material layer 25 isformed on the nonmagnetic layer 70. There is no particular limitationplaced on a material and a structure of this ferromagnetic materiallayer 25. A continuous single layer may be used or a patterned medium asdescribed in the first embodiment may be formed. Alternatively, anmultilayer film as described in the second embodiment may be formed. Inaddition, the ferromagnetic material layer 25 may be set as a recordinglayer of a normal longitudinal recording system or as a recording layerof a perpendicular recording system. Thus, the magnetic recording mediumwith the deep layer servo system is obtained.

In the magnetic recording medium with the deep layer servo system, sinceservo information is written in the servo layer 60 independent of therecording layer 25, the servo information can be written on a fullsurface of the servo layer 60. Accordingly, positioning control can becarried out with high accuracy. On the other hand, the quantity of servoinformation to be written is greatly increased. However, by using themanufacturing method of the above-described fourth embodiment, sinceservo information can be written all at once, it is possible to greatlyshorten the manufacturing process.

Hereinafter, description will be made for examples of the fourthembodiment, which are made by the inventors.

EXAMPLE 9

A deep layer servo region was formed by using a method similar to thatof the example 7. That is, CoPt was deposited by about 20 nm on asubstrate by a sputtering method. Then, a resist film was coated in athickness of about 1.0 μm on the CoPt film, and through batch exposureand development, an opening pattern equivalent to the wedge-shaped servopattern shown in FIG. 7A was formed in the resist film. Subsequently, asurface of the sample was exposed in F radicals for about 30 secondswhile being maintained at room temperature. Then, the resist was removedby using an oxygen ashing apparatus.

Then, SiO2 was deposited by 500 nm on the servo layer by a sputteringmethod, and CoPt to be a recording layer was further deposited by 50 nmby a sputtering method. Accordingly, a magnetic recording medium havinga deep layer servo structure was obtained.

FIFTH EMBODIMENT

A fifth embodiment relates to a magnetic recording device (HDD: harddisk drive) equipped with the magnetic recording medium of one of theabove-described first to fourth embodiments.

FIG. 11 is a perspective view showing an example of a structure of a HDDaccording to the fifth embodiment. As shown in FIG. 11, a magneticrecording medium 100 is mounted on a spindle 101, and rotated by anot-shown motor. An actuator arm 102 attached to a fixed shaft 103 has asuspension 104 in its tip, and a head slider 105 is provided in a tip ofthis suspension 104.

In a base end of the actuator arm 102, a voice coil motor 106 as a typeof a linear motor is provided. This voice coil motor 106 includes amagnetic circuit which is composed of a not-shown driving coil wound upon a bobbin portion of the actuator arm 102, and a permanent magnet andan opposite yoke which are disposed oppositely so as to each other tosandwich the coil.

A not-shown recording/reproducing head is formed in a tip of the headslider 105. By rotation of a disk, the head slider 105 is floated bykeeping a fixed distance with the magnetic recording medium 100, and therecording/reproducing head is moved relatively to the magnetic recordingmedium 100. In recording, information is recorded in the magneticrecording medium 100 by a magnetic field generated from the recordinghead. In reproducing information, by scanning of the reproducing head onthe magnetic recording medium, information is reproduced by a leakagemagnetic field from each bit on the magnetic recording medium.

FIG. 12 is a perspective view showing a structure of another HDD of theembodiment. In the case of the above-described HDD shown in FIG. 11, themagnetic recording medium is rotated, and recording/reproducing iscarried out by the floating type magnetic head. However, when arecording density of the magnetic recording medium becomes much higher,an influence of shaft vibration along with the rotation of the recordingmedium cannot be ignored. On the other hand, in the case of the HDDshown in FIG. 12, no shaft vibration problem occurs because rotarydriving is not used.

A magnetic recording medium 202 is loaded on a stage 203 which can bedriven in X, Y and Z directions. A head portion 201 including aplurality of magnetic heads is disposed oppositely to the magneticrecording medium. The head portion 201 is fixed, and the magneticrecording medium 202 is moved relatively to the head portion 201 bydriving of the stage 203 using a piezo element. Since no rotary-drivingis carried out, the magnetic recording medium needs not be disk-shaped,and a rectangular-shape one or the like can be used as shown in thedrawing.

The head portion 201 includes the plurality of heads disposed in amulti-array form, and by simultaneously recording/reproducing aplurality of information, it is possible to execute high-speed andlarge-capacity data recording/reproducing. No particular limitation isplaced on the number of heads.

There is no particular limitation on a method of recording informationin the magnetic recording medium. A method of writing by a leakagemagnetic field from the head, a method of writing by a magnetic fieldformed by a current flowing due to charge injection by a needle-shapedprobe, and the like may be used.

There is also no particular limitation on a method of reproducinginformation of the magnetic recording medium. A method of detecting aleakage magnetic field of the magnetic recording medium, a method ofdetecting spinning of a tunnel current of the recording medium, and thelike may be used.

If the above-described HDD is equipped with the patterned medium of thefirst or the second embodiment, a device which is high in a SN ratio,large in capacity and low in manufacturing costs can be provided.Moreover, if the HDD is equipped with the magnetic recording medium ofthe third or the fourth embodiment, manufacturing costs can be reducedby shortening the time of writing servo information. Especially, if themagnetic recording medium of the deep layer servo system of the fourthembodiment is used, a large storage capacity and highly accuratepositioning control can be provided.

SIXTH EMBODIMENT

A sixth embodiment relates to patterning of a magnetic material otherthan a magnetic recording medium, especially to patterning of a magneticrandom access memory (MRAM).

The magnetic material patterning method of each of the above-describedfirst to fourth embodiments can be used for fabricating various magneticproducts which require patterning of magnetic materials other than themagnetic recording medium, the products being, for example, an MRAM, amotor, a magnetic sensor, a magnetic switch and the like.Conventionally, in the manufacturing methods of these magnetic productsphysical etching such as ion milling has mainly been used forfabricating a hard magnetic material layer. If a method of changing anunnecessary magnetic material region to a nonmagnetic material by usinghalogenation reaction is used instead, property deterioration of themagnetic material layer, caused by physical damage, can be prevented.

Especially, in the manufacturing method of the MRAM where integrationand mass production are required, an advantage obtained by applying themagnetic material patterning method of each of the first to fourthembodiments is large. The MRAM is one obtained by applying a technologyof magnetic tunnel junction to a random access memory, and has amagnetic tunnel junction element structure composed of two ferromagneticmaterial layers and a thin insulating layer sandwitched therebetween.Compared with a conventional DRAM, the MRAM is more advantageous in thatthe MRAM can be used as a nonvolatile memory and has a high accessspeed. High integration is necessary for securing a large memorycapacity, and in a manufacturing process thereof, microfabrication andsimplification of the process are required.

FIGS. 13A to 13C show an MRAM patterning process of the sixthembodiment. Here, only one memory element is shown; however, in anactual product, similar memory elements are arrayed on the samesubstrate in a matrix form.

First, as shown in FIG. 13A, on a Si substrate 310 having, for example,a thermal oxide film formed thereon, a buffer layer 320, a lowerferromagnetic material layer 330, a tunnel oxide layer 340, and an upperferromagnetic material layer 350 are sequentially laminated. A patternof resist 360 is further formed on the laminated surface. A plurality ofbuffer layers and an electrode layer may be provided between the Sisubstrate 310 and the lower ferromagnetic material layer 320. Inaddition, for the lower and upper ferromagnetic material layers 330 and350, as described in the first embodiment, various ferromagneticmaterials containing any of elements Fe, Ni and Co, in composition, canbe used.

A surface layer is exposed in active reaction gas containing halogen gassuch as fluorine radicals under conditions similar to those of the firstembodiment. Then, the remaining resist is removed by oxygen ashing. Asshown in FIG. 13B, a region not covered with a mask of the resist 360 ishalogenated from the upper ferromagnetic material layer 350 to the lowerferromagnetic material layer 330, and then changed to a halide 370 as anonferromagnetic insulating layer.

Then, by using a normal semiconductor process to form a pattern of anupper electrode layer 380 on a recording region layer, a MRAM structureshown in FIG. 13C is obtained.

By using the patterning method of the sixth embodiment, it is possibleto separate the respective memory element regions including the upperferromagnetic material layer 350, the tunnel oxide layer 340 and thelower electrode layer 330 by a chemical method without etching step.

If fabrication is carried out by physical etching using the conventionalion milling method, depending on an incident angle of Ar ions,short-circuiting often occurs in the side wall of the upperferromagnetic material layer 350, the tunnel oxide layer 340 and thelower electrode layer 330 constituting junction. Because there arearticles reattached on a surface by milling. However, by using themagnetic material patterning method of the sixth embodiment, not onlydamage caused by the physical etching, but also short-circuiting or thelike between the upper and lower ferromagnetic material layers 330 and350, caused by residuals after the etching, can be prevented.

In addition, since the halogenation reaction is used, resist which canbe subjected to oxygen ashing can be used. If a self-organization resistsuch as a diblock copolymer is used as the resist, fine patterns can beformed in a large area all at once. Thus, higher integration can beachieved more easily.

Also, magnetic tunnel junction which can be applied to a reproducingmagnetic head or the like can be provided by using a similar magneticmaterial patterning method.

Hereinafter, description will be made for an example of the sixthembodiment, which is made by the inventors.

EXAMPLE 10

Referring again to FIGS. 13A to 13C, description will be made for amagnetic material patterning method of an example 10 of the sixthembodiment.

First, as a buffer layer 320, an NiFe film was formed in a thickness ofabout 20 nm on a Si substrate 310 having a thermal oxide film by asputtering method. Subsequently, on the buffer layer 320, a Co filmhaving a thickness of about 4 nm as a lower ferromagnetic material layer330. Al₂O₃ having a thickness of about 1 nm as a tunnel oxide layer, anda Co film having a thickness of about 10 nm as an upper ferromagneticmaterial layer 350 were sequentially laminated; Then, resist was coatedin a thickness of about 1 μm on a surface of the upper ferromagneticmaterial layer 350 by spin coating, and through batch exposure anddevelopment, a square resist mask pattern of 5.0 μm×5.0 μm was formed.

By using an ICP apparatus, the substrate was exposed in generated Fradicals for about 3 minutes. An exposed region not covered with theresist mask was analyzed by using AES, and presence of CoF₂ wasverified. As a result of measuring a change with passage of time in apeak of CoF₂ while sputtering, presence of CoF₂ up to a depth of 15 nmfrom the surface was verified. In other words, conversion of alljunction portions (Co:4 nm/Al₂O₃:1 nm/Co:10 nm) into halides wasverified.

Subsequently, the resist was removed by O₂ ashing, and then a Cu filmwas formed in a thickness of about 300 nm as an upper electrode layer380. For patterning, a metal mask was used.

In order to investigate whether or not short-circuiting occurs in theside face of junction, resistance values before and after fabricationwere measured. When values standardizing the respective resistancevalues with a junction portion area were R₀ and R₁, R₁/R₀=1 wasestablished. Based on the above result, occurrence of noshort-circuiting was verified. In addition, the prepared sample showed R(resistance value)=1.7×10⁶ Ω, and MR=10%.

The MRAM fabricated in the above-described manner exhibited a resistancevalue and an MR ratio approximately equal to those of the MRAMfabricated by the normal ion milling, indicating that the magneticmaterial patterning method of the sixth embodiment was also effective asthe MRAM fabrication method.

The description has been hereinbefore made for the magnetic recordingmedium and its manufacturing method of the present invention accordingto the respective embodiments. However, it should be understood that thepresent invention is not limited to the embodiments described above.Modifications and variations of the embodiments described above willoccur to those skilled in the art, in light of the above teaching.

1. A magnetic storage medium comprising: a substrate; a plurality ofrecording regions formed on the substrate and made of ferromagneticmaterials, each containing at least one element selected from the groupconsisting of Fe, Co and Ni; and a nonferromagnetic material region madeof a compound of the ferromagnetic material and halogen, thenonferromagnetic material region is adjacent to the recording regionsand separates the recording regions from each other.
 2. The magneticstorage medium of claim 1, wherein the halogen is fluorine.
 3. Themagnetic storage medium of claim 2, wherein the compound is a cobaltfluoride.
 4. A magnetic storage medium comprising: a servo layercomprising; a substrate: a plurality of recording regions formed on thesubstrate and made of ferromagnetic materials, each containing at leastone element selected from the group consisting of Fe, Co and Ni; and anonferromagnetic material region made of a compound of the ferromagneticmaterial and halogen, the nonferromagnetic material region is adjacentto the recording regions and separates the recording regions from eachother.
 5. The magnetic storage medium of claim 4, further comprising: anonmagnetic material layer formed on the servo layer; and a recordinglayer formed on the nonmagnetic material layer.
 6. The magnetic storagemedium of claim 4, wherein the halogen is fluorine.
 7. The magneticstorage medium of claim 6, wherein the compound is a cobalt fluoride.